The header contains identifiers for one or more digest algorithms that the sender wishes the responder to use to create the digest. The sender may use quality values to indicate its preference ordering among the choices it offers.
Want-Digest does not include any digest algorithms that the server
supports, the server may respond with:
- a digest calculated using a different digest algorithm, or
400 Bad Requesterror, and include another
Want-Digestheader with that response, listing the algorithms that it does support.
See the page for the
Digest header for more
|Header type||Request header, Response header|
|Forbidden header name||no|
Want-Digest: <digest-algorithm> // Multiple algorithms, weighted with the quality value syntax: Want-Digest: <digest-algorithm><q-value>,<digest-algorithm><q-value>
- Supported digest algorithms are defined in RFC 3230 and RFC 5843, and include
SHA-512. Some of the supported algorithms, including
MD5are subject to collisions and are thus not suitable for applications in which collision-resistance is important.
- The quality value to apply to that option.
Want-Digest: sha-256 Want-Digest: SHA-512;q=0.3, sha-256;q=1, md5;q=0
The sender provides a list of digests which it is prepared to accept, and the server uses one of them:
Request: GET /item Want-Digest: sha-256;q=0.3, sha;q=1 Response: HTTP/1.1 200 Ok Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
The server does not support any of the requested digest algorithms, so uses a different algorithm:
Request: GET /item Want-Digest: sha;q=1 Response: HTTP/1.1 200 Ok Digest: sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
The server does not support any of the requested digest algorithms, so responds with a
400 error and includes another
Want-Digest header, listing the algorithms
that it does support:
Request: GET /item Want-Digest: sha;q=1 Response: HTTP/1.1 400 Bad Request Want-Digest: sha-256, sha-512
|Resource Digests for HTTP|
This header was originally defined in RFC 3230, but the definition of "selected representation" in RFC 7231 made the original definition inconsistent with current HTTP specifications. When released, The "Resource Digests for HTTP" draft therefore will obsolete RFC 3230 and will update the standard to be consistent.
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